Esber, R. 2023. Toxicity of Some Inert Dusts and Ash Against Rice Weevil, Sitophilus oryzae L. Under Laboratory Conditions. Arab Journal of Plant Protection, 41(4): 398-405. https://doi.org/10.22268/AJPP-41.4.398405 A study was carried out to assess the toxicity of kaolin, silica and apple ash against adults of rice weevil, Sitophilus oryzae L. (Curculionidae: Coleoptera) using three concentrations: 2, 4 and 8 g inert material/100 g of wheat grains. Insect mortality was assessed 1, 2, 3, 4, 6, 8 and 10 days after treatment, and corrected mortality rate was calculated, as well as the LC50 and LC90, and the LT50 and LT90 values. The results obtained showed an increase in the mean of corrected mortality rate with increasing concentration and treatment time, whereas mortality rates reached at the concentration of 8g/100g grains after 10 days of treatment with kaolin, silica and apple ash 93, 48.15 and 100%, respectively, with significant superiority of apple ash over each of kaolin and silica. The LC50 and LC90 values 10 days after treatment were as follows: 1.68 and 6.26 g/100 g for kaolin, 8.69 and 24.55 g/100 g for silica, and 0.95 and 2.92 g/100 g for apple ash, respectively. Whereas, the values of LT50 and LT90 for kaolin were 2.72 and 4.89 days, 6.09 and 10.68 days for silica, and 2.81 and 4.17 days for apple ash, respectively, at 8g/100g seeds. The results obtained showed that kaolin had the highest toxicity three days after treatment, and the values were close to that of apple ash at 4 and 6 days after treatment, with significant difference with silica dusts, whereas apple ash achieved the highest toxicity with a significant difference compared with both kaolin and silica dusts, 10 days after treatment. Keywords: Toxicity, powder, inert dusts, ash, kaolin, silica, apple ash, rice weevil, Sitophilus oryzae